Tunnel portal light and shade excavation combined semi-light and semi-dark structure and construction method thereof

Abstract

The invention discloses a tunnel portal light and shade excavation combined semi-bright and semi-dark structure and a construction method thereof.The tunnel portal light and shade excavation combined semi-bright and semi-dark structure is characterized in that a cover arch is arranged at a tunnel portal, and a guide pipe is arranged in the range of the 60-degree angle of the side, adjacent to a mountain, of the cover arch; the pipe shed comprises a steel pipe, and the steel pipe is driven into surrounding rock along the guide pipe; the open-cut section lining structure comprises an open-cut section right-angle inverted arch, an open-cut section lining and an expanded foundation. The underground excavation section lining structure comprises an underground excavation section primary support and an underground excavation section secondary lining, the underground excavation section secondary lining is located on the inner layer of the underground excavation section primary support, and the underground excavation section primary support and the underground excavation section secondary lining are connected with the open excavation section lining; and the back pressure backfilling structure is arranged on the outer sides of the open cut section right-angle inverted arch, the open cut section lining and the enlarged foundation. The structure stability and the construction safety of the tunnel portal can be fully guaranteed.

Description

Technical Field

[0001] The present application belongs to the technical field of tunnel construction, and specifically relates to a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance and a construction method thereof. Background Art

[0002] When the tunnel entrance section passes through the terrain with higher terrain on the adjacent mountain side and shallow terrain on the distant mountain side, half of the tunnel structure is buried deep underground and the other half is exposed outside the surface, forming a special structure that is half bright and half dark.

[0003] The shallow terrain and soft soil increase the construction difficulty and risk. Therefore, under the restrictions of this terrain and poor geological conditions, the traditional fully enclosed tunnel boring method is no longer applicable. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present application provides a semi-open and semi-dark structure of a tunnel entrance that combines open and concealed excavation and a construction method thereof. Taking into account the relative relationship between the tunnel entrance terrain and the tunnel structure, as well as the safe construction process, a phased construction method is adopted according to the particularity of the semi-open and semi-dark terrain of the tunnel entrance section.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] A semi-open and semi-hidden structure combining open and hidden excavation at the tunnel entrance, comprising:

[0007] A sleeve arch is arranged at the tunnel entrance, and a guide tube is provided on the sleeve arch within a 60° angle range on the side adjacent to the mountain;

[0008] A pipe shed comprises steel pipes, which are driven into the surrounding rock along the guide pipe;

[0009] Cut-and-cover lining structure, including cut-and-cover right-angle invert, cut-and-cover lining and expanded foundation;

[0010] The underground excavation lining structure includes an underground excavation primary support and an underground excavation secondary lining, wherein the underground excavation secondary lining is located within the inner layer of the underground excavation primary support, and the underground excavation primary support and the underground excavation secondary lining are connected to the open excavation lining; and

[0011] The counter-pressure backfill structure is arranged outside the right-angle inverted arch of the open-cut section, the lining of the open-cut section and the expanded foundation.

[0012] Furthermore, three I-beams are arranged in the sleeve arch; the diameter of the guide tube is 100-150 mm; the three I-beams and the guide tube are welded into a whole.

[0013] Furthermore, the open-cut section lining structure is provided with first, second, third and fourth steel bars at intervals in a circumferential direction at right angles from the arch top to the arch foot, and fifth, sixth, seventh and eighth steel bars are provided at intervals in a circumferential direction at right angles from the arch bottom to the arch foot; the second, third, fourth, fifth, sixth and seventh steel bars all exceed the open-cut section lining structure;

[0014] The first steel plates are arranged at intervals along the tunnel direction on the vault cross section of the open-cut section lining;

[0015] The bottom cross section of the right-angled inverted arch in the open-cut section is provided with second steel plates at intervals along the tunnel direction;

[0016] The open cut section lining structure is further provided with one row of ninth steel bars and two rows of tenth steel bars at intervals;

[0017] In each interval, the first steel bar and the ninth steel bar are welded to the first steel plate, and the eighth steel bar and the tenth steel bar are welded to the second steel plate.

[0018] Furthermore, the lining structure of the underground excavation section is provided with an eleventh steel bar, a twelfth steel bar and a thirteenth steel bar at intervals in a circumferential direction from the arch top to the arch foot; and a fourteenth steel bar, a fifteenth steel bar and a sixteenth steel bar are provided at intervals in a circumferential direction from the arch bottom to the arch foot.

[0019] In each interval, the eleventh, twelfth and thirteenth steel bars are respectively welded to the second, third and fourth steel bars, and the fourteenth, fifteenth and sixteenth steel bars are respectively welded to the fifth, sixth and seventh steel bars.

[0020] In addition, the present application also provides a construction method for a semi-open and semi-hidden structure of a tunnel entrance combining open and hidden excavation, comprising:

[0021] The slope of the mountain outside the tunnel entrance and between the entrance stake and the light-dark boundary stake shall be set at 1:0.5;

[0022] A sleeve arch is constructed at the tunnel entrance, and a guide pipe is provided within a 60° angle on the side adjacent to the mountain;

[0023] A pipe shed is constructed on the sleeve arch, and steel pipes of the pipe shed are driven into the surrounding rock along the guide pipe;

[0024] The open cut section is constructed to form an open cut section lining structure, wherein the open cut section lining structure includes an open cut section right-angle invert arch, an open cut section lining and an expanded foundation;

[0025] The counter-pressure backfill construction forms a counter-pressure backfill structure, wherein the counter-pressure backfill structure is arranged outside the right-angle inverted arch of the open-cut section, the lining of the open-cut section and the expanded foundation; and

[0026] The construction of the dark excavation section forms a dark excavation section lining structure, which includes the dark excavation section initial support and the dark excavation section secondary lining. The dark excavation section secondary lining is located in the inner layer of the dark excavation section initial support, and the dark excavation section initial support and the dark excavation section secondary lining are connected to the open excavation section lining.

[0027] Furthermore, the open-cut section construction includes:

[0028] First, the surrounding rock of the exposed section of the structure is excavated using the step method and vertical temporary supports are set up;

[0029] Under the protection of the pipe roof and the vertical temporary support, the open-cut section lining structure is cast; the open-cut section lining structure is provided with first, second, third and fourth steel bars at intervals in a circumferential direction at right angles from the arch top to the arch foot; the open-cut section lining structure is provided with fifth, sixth, seventh and eighth steel bars at intervals in a circumferential direction at right angles from the arch bottom to the arch foot; the second, third, fourth, fifth, sixth and seventh steel bars all exceed the open-cut section lining structure; the open-cut section lining structure is also provided with a row of ninth steel bars and two rows of tenth steel bars at intervals;

[0030] Pre-embedding first steel plates at intervals along the tunnel direction in the arch top section of the open-cut section lining, and pre-embedding second steel plates at intervals along the tunnel direction in the arch bottom section of the right-angle inverted arch of the open-cut section; and

[0031] In each interval, the first steel bar, the ninth steel bar and the first steel plate are welded, and the eighth steel bar, the tenth steel bar and the embedded second steel plate are welded.

[0032] Furthermore, the provision of vertical temporary support includes:

[0033] 16 I-steel arch frames are installed at intervals within the main body of the vertical temporary support;

[0034] Use 22mm diameter locking coil anchor rods to cross and weld at intervals at both ends of the vertical temporary support body to form a whole; and

[0035] The middle of the vertical temporary support body is welded with 22mm diameter early strength drug-coated anchor rods at intervals, thus forming a whole with the surrounding rock.

[0036] Furthermore, the underground excavation construction includes:

[0037] The tunnel construction is carried out using the fully enclosed underground excavation method, and initial support for the underground excavation section is provided;

[0038] removing the vertical temporary supports; and

[0039] The secondary lining of the concealed excavation section is integrally molded; the eleventh steel bar, the twelfth steel bar and the thirteenth steel bar are circumferentially arranged at intervals from the arch top to the arch foot of the secondary lining of the concealed excavation section; the fourteenth steel bar, the fifteenth steel bar and the sixteenth steel bar are circumferentially arranged at intervals from the arch bottom to the arch foot; in each interval, the eleventh steel bar, the twelfth steel bar and the thirteenth steel bar are respectively welded to the second steel bar, the third steel bar and the fourth steel bar, and the fourteenth steel bar, the fifteenth steel bar and the sixteenth steel bar are respectively welded to the fifth steel bar, the sixth steel bar and the seventh steel bar.

[0040] Furthermore, the surrounding rock of the exposed section of the structure is first excavated using a step method, and vertical temporary support is set up, including:

[0041] Excavate the upper surrounding rock of the open cut section;

[0042] Construct temporary vertical support on the upper part of the open cut section;

[0043] Excavation of the surrounding rock below the open cut section; and

[0044] Construct vertical temporary support at the bottom of the open cut section;

[0045] Before each excavation, hollow grouting anchor rods are used to reinforce the surrounding rock in front of the adjacent mountain side.

[0046] Furthermore, the tunnel construction is carried out by adopting the fully enclosed underground excavation method and setting up the initial support of the underground excavation section, including:

[0047] Excavate the upper surrounding rock of the underground excavation section;

[0048] Carry out initial support on the upper part of the underground excavation section;

[0049] Excavation of the upper surrounding rock of the underground excavation section; and

[0050] Carry out initial support on the upper part of the underground excavation section.

[0051] Compared with the prior art, this application has the following advantages:

[0052] This application solves the problem that when the tunnel portal section passes through the terrain of the adjacent mountain side is higher and the distant mountain side is shallower, half of the tunnel structure is buried deep underground and the other half is exposed outside the surface, resulting in the traditional fully enclosed tunnel excavation method being no longer applicable.

[0053] This application first uses the open-cut method to complete the tunnel structure of the exposed section and backfill it, and then carries out the remaining tunnel excavation and structural construction under the formed dark-cut construction conditions, which can fully ensure the structural stability of the tunnel entrance and the safety of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application but do not constitute an improper limitation on the present application. In the drawings:

[0055] Figure 1 This is a schematic diagram of the mountain outside the cave and between the cave entrance and the light-dark boundary;

[0056] Figure 2 This is a schematic diagram of constructing the sleeve arch;

[0057] Figure 3 This is a cross-sectional view of a long tube shed;

[0058] Figure 4 This is a schematic diagram of the reinforcement of the long pipe shed within the 60° range;

[0059] Figure 5 Design drawings of the right-angle tunnel lining structure with expanded foundation for open-cut construction;

[0060] Figure 6 Schematic diagram of the overall structure of the right-angle tunnel lining and temporary support for the expanded foundation constructed using the open-cut method;

[0061] Figure 7 Design drawings for the reinforcement of the open-cut section structure;

[0062] Figure 8 Design drawing for hanging formwork of metal corrugated plate;

[0063] Figure 9 The first steel plate is embedded, and B is the fixing design drawing, where (a) is the welding diagram of the steel bar and the first steel plate, (b) is the welding diagram of the steel bar and the second steel plate, (c) is the first steel plate, and (d) is the second steel plate;

[0064] Figure 10 This is a schematic diagram of back pressure backfill;

[0065] Figure 11 This is the design drawing of the composite lining structure and reinforcement of the underground excavation section. DETAILED DESCRIPTION

[0066] In order to enable people skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0067] In the description of this application, it should be understood that the orientation or positional relationship indicated by terms and the like is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device, element, module, system, platform or device referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. The following description of this application is only to be understood as a description of individual embodiments of the technical solution of this application. Other embodiments are not reflected in the following description, but it does not mean that this application excludes these other embodiments, and the technical solution of this application is not limited to the specific implementation methods described below, and the scope of protection of this application is not limited to only the specific implementation methods described below. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of this application.

[0068] It should be noted that, if the terms "first", "second", etc. appear in the specification and claims of the present application and the above-mentioned drawings, the description is only used to distinguish similar objects and is not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in a sequence other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0069] The structural design and construction process of this application mainly include the following points:

[0070] 1. The mountain outside the tunnel entrance and between the entrance pile number and the light and dark boundary pile number shall be sloped at a ratio of 1:0.5, leaving working space for the tunnel entrance and the arch structure.

[0071] 2. Construct a 200cm long and 80cm thick arch structure. Reserve long pipe guide pipes in the half of the arch on the mountain side, with a circumferential spacing of 40cm.

[0072] 3. Continue to construct a long pipe shed inside the guide pipe. The effective length should reach the pile number where the ground line meets the tunnel structure + 100cm and ≥20m.

[0073] 4. A 76cm-thick, expanded foundation, right-angle reinforced concrete lining will be constructed in the exposed section between the light-dark boundary stake and the ground line, connecting the tunnel structure. A waterproof layer will be applied to the exterior surface, along with 150mm-diameter annular drainage blind pipes spaced 5m apart. After reaching the design strength, a 2.5-10m depth of backfill will be applied to the exterior of the structure.

[0074] 5. When the conditions for underground excavation are formed, the remaining surrounding rock is excavated by underground excavation method and the primary support + secondary lining structure is constructed.

[0075] In some embodiments, as Figure 1 As shown, the mountain outside the tunnel entrance and between the entrance stake and the light-dark boundary stake is sloped at a ratio of 1:0.5 to form a slope line 13, and slope reinforcement and protection are implemented. After this section of soil is cleared, ample space will be left for the tunnel entrance and the arch structure. The excavated mountain 1 has a ground line 12 at the entrance stake and a ground line 11 at the light-dark boundary stake, and is located within the mountain surrounding rock 2.

[0076] like Figure 2 As shown, a sleeve arch 15 is constructed. The sleeve arch structure is 200 cm long and 80 cm thick. Three I-beams 14 are installed within the arch. Eighteen guide tubes 16 with a diameter of 133 cm are arranged at a 1° external angle within a 60° range on the mountain side. During construction, these guide tubes are driven into the surrounding rock mass 2, forming an effective reinforcement zone. A core soil 17 is reserved in the center. The guide tubes 16 are spaced 40 cm apart circumferentially and welded to the I-beams 14 to form a single piece.

[0077] like Figure 3-Figure 4 As shown, a long pipe shed 18 is constructed. During the construction of the first ring of pipe shed 18, the casing arch 15 must be kept stable and prevented from shifting or settling. Temporary supports may be added if necessary to ensure that the steel pipes of pipe shed 18 are smoothly and accurately driven into the surrounding rock mass 2 along the guide tubes 16 within casing arch 15. The effective length of long pipe shed 18 should extend from the ground line to the pile number where the tunnel structure meets the ground line, and should extend 1 meter vertically, but should not be less than 20 meters.

[0078] Then, if Figure 5-Figure 6 Carry out open-cut construction of exposed structural sections, construction process and corresponding parts ①-⑤:

[0079] 1) First, the surrounding rock of the exposed section of the structure is excavated using the step method. The main steps are as follows: excavate the upper surrounding rock I of the open cut section, use a small advance grouting pipe 116 with a diameter of 42 to provide advance support for the side of the open cut section near the mountain, excavate the upper surrounding rock I of the open cut section, and make the upper half of the open cut section I advance the lower half of the open cut section II by 5m; construct vertical temporary support ① for the upper part of the open cut section, set 16 I-shaped steel frames in the support wall, wherein the longitudinal spacing of the steel frames is 60cm, and the upper and lower ends are welded to a whole with steel bars 114 provided by cross-driven anchor rods driven into the surrounding rock; excavate the lower surrounding rock II of the open cut section; construct vertical temporary support ② for the lower part of the open cut section, after the upper half of the open cut section I is excavated forward for 5m, excavate the lower surrounding rock II of the open cut section and construct vertical temporary support wall ② for the lower part of the open cut section, wherein the upper end of the steel frame is connected to the bottom end anchor bolt of the steel frame in ①, and the lower end is welded to the steel bar 114 provided by cross-driven anchor rods driven into the surrounding rock as a whole. Before each excavation, hollow grouting anchor rods with a diameter of 42mm should be used to grout and reinforce the surrounding rock in front of the adjacent mountain side, and the initial support and advance support should be repeated. The excavation progress of each cycle should be controlled at the distance between one arch frame.

[0080] 2) Under the protection of the pipe-roof support ring and vertical temporary supports 118, the open-cut lining structure 112 was cast. The main steps were: formwork casting of the open-cut right-angle inverted arch ③ and expanded foundation ④; reinforcement and leveling of the exposed expanded foundation right-angle tunnel lining ③ and ④ subgrade; formwork casting of the open-cut lining ⑤, 76 cm thick; tying of the reinforcement for the open-cut right-angle tunnel lining ③ and ⑤; and formwork casting of the open-cut right-angle inverted arch ③ and arch haunch ⑤. During casting, grooves for welding the first and second steel plates 111 and 119 were reserved at the junction of the semi-exposed and semi-concealed structures, i.e., at the arch crown and arch base sections of the lining. The reserved grooves were slightly larger than the steel plate dimensions. Class A adhesive was applied to the grooves to bond the pre-embedded first and second steel plates 111 and 119, and then perforated and plug-welded to the tunnel lining reinforcement. A plain concrete expanded foundation ④ was cast, 3 m wide and 2.5 m high. When the vertical temporary support 118 undergoes a large displacement during construction, a bottom diagonal brace should be installed.

[0081] 3) Set up a 16-inch I-steel arch frame 117 within the main body of the vertical temporary support 118. Use the tail ends of 22mm diameter locking anchor rods 114 to cross-weld the ends of the steel arch frames in temporary support ① and ② to form a single unit. The middle section is welded to the tail ends of 22mm diameter early-strength anchor rods 115 to form a single unit with the surrounding rock. The I-steel should be set as close to the excavated rock face as possible and connected longitudinally with 22mm diameter steel bars. The steel mesh is welded to the steel frame, and then concrete is sprayed to form the support wall.

[0082] 4) Pre-embed steel plates at the junction of the semi-visible and semi-concealed structures. Specifically, a first steel plate 111 (40×26×2cm) was embedded in the lining's arch section, and a second steel plate 119 (40×45×2cm) was embedded in the arch section, with longitudinal center spacing of 0.6m. A waterproof layer and 150mm diameter annular drainage blind pipes were laid on the exterior surface, with longitudinal spacing of 5m.

[0083] 5) In particular, the reinforcement of the open-cut lining structure 112 in the present invention requires special design. Four steel bars, namely the first steel bar N1, the second steel bar N2, the third steel bar N3, and the fourth steel bar N4, are circumferentially arranged from the arch crown to the arch foot. Four steel bars, namely the fifth steel bar N5, the sixth steel bar N6, the seventh steel bar N7, and the eighth steel bar N8, are circumferentially arranged from the arch bottom to the arch foot. A row of 50 cm-long steel bars, namely the ninth steel bar N9, and two rows of 50 cm-long steel bars, namely the first and tenth steel bars N10, are added to the partially embedded steel plate. The first and ninth steel bars N1 and N9 are welded to the embedded first steel plate 111 using perforated plug welding 130. The eighth steel bar N8, along with the first and tenth steel bars N10, are welded to the embedded second steel plate 119 using perforated plug welding 130. The second steel bar N2, the third steel bar N3, the fourth steel bar N4, the fifth steel bar N5, the sixth steel bar N6, and the seventh steel bar N7 exceed the lining structure by 150cm and are used to weld the circumferential steel bars of the secondary lining structure of the hidden excavation into a whole. The longitudinal spacing of the circumferential steel bars is 20cm. Figure 7 、 Figure 8 、 Figure 9 .

[0084] In particular, this is an open-cut section, and erecting the tunnel lining formwork is one of the difficulties. This application adopts metal corrugated plate hanging formwork technology, which can quickly form the formwork and ensure that the lining surface is relatively smooth. The metal corrugated plate formwork 124 is a prefabricated formwork and needs to be processed in advance according to the inner / outer surface contours of the lining. The width of each ring of the metal corrugated plate formwork 124 is 70 cm, which is consistent with the 60 cm spacing of the vertical temporary wall protection I-beam frame. The extra 10 cm is used for welding and connection with adjacent corrugated plates. The lower part of the inner metal corrugated plate formwork is hoisted by steel rope 128, and the two ends of the steel rope 128 are respectively welded to the wall protection I-beam frame and the metal corrugated plate, and steel pipe 127 is arranged horizontally for support. The top also uses steel pipe 126 diagonal bracing to ensure that it can fully bear the weight of the concrete during pouring. The inner and outer metal corrugated plates are rigidly connected with steel bars 125 to form a whole that can be poured.

[0085] 6) When the open cut section is fully constructed and reaches the designed strength, backfilling is carried out with a backfill height of 2.5m to 10m. Figure 10 shown.

[0086] Then, if Figure 11 The dark tunnel structure is constructed using the dark excavation method shown in the figure. The construction process and corresponding parts ⑥-⑧ are as follows:

[0087] 1) After the open-cut tunnel structure is constructed and backfill is backfilled, the remaining surrounding rock meets the conditions for fully enclosed tunnel construction, and tunnel construction can be carried out using the tunnel method. The main construction steps are: excavation of the upper surrounding rock of the tunnel section III; installation of the upper primary support of the tunnel section ⑥; excavation of the upper surrounding rock of the tunnel section IV; installation of the upper primary support of the tunnel section ⑦; removal of the vertical temporary supports ① and ②, and integral formwork construction of the secondary lining ⑧.

[0088] 2) The initial support for the dark excavation section consists of 26cm-thick C25 shotcrete, containing 20a I-beam arches with a longitudinal spacing of 0.6m. The ends of the initial support ⑥ steel arches are welded to the embedded first steel plate 111, and the ends of the initial support ⑦ steel arches at the arch bottom are welded to the embedded second steel plate 119.

[0089] 3) In particular, the reinforcement of the concealed excavation lining structure in this invention requires special design. The concealed excavation secondary lining is 40 cm thick. The circumferential reinforcements (N11, N12, and N13) are welded to the circumferential reinforcements (N2, N3, and N4) of the open-excavation structure. The circumferential reinforcements (N14, N15, and N16) are welded to the circumferential reinforcements (N5, N6, and N7) of the open-excavation structure, respectively. The overlap lengths are all 150 cm.

[0090] In some embodiments, as Figures 1-11 As shown, the above construction method can be used to obtain a semi-open and semi-dark structure of a tunnel entrance that combines open and dark excavation, including:

[0091] A sleeve arch 15 is provided at the tunnel entrance, and a guide tube 16 is provided at a 60° angle on the side adjacent to the mountain;

[0092] The pipe shed 18 comprises steel pipes, which are driven into the surrounding rock along the guide pipe 16;

[0093] The open-cut lining structure 112 includes an open-cut right-angle invert arch, an open-cut lining 120 and an expanded foundation 113;

[0094] The underground excavation lining structure includes an underground excavation primary support 122 and an underground excavation secondary lining 123, wherein the underground excavation secondary lining 123 is located inside the underground excavation primary support 122, and the underground excavation primary support 122 and the underground excavation secondary lining 123 are connected to the open excavation lining 120; and

[0095] The counter-pressure backfill structure 131 is arranged outside the right-angled inverted arch of the open-cut section, the open-cut section lining 120 and the expanded foundation 113.

[0096] In some embodiments, three I-beams 14 are provided in the sleeve arch 15; the diameter of the guide tube 16 is 100-150 mm; the three I-beams 14 and the guide tube 16 are welded into a whole.

[0097] In some embodiments, the open-cut lining structure 112 is provided with four steel bars, namely, a first steel bar N1, a second steel bar N2, a third steel bar N3, and a fourth steel bar N4, at intervals in a circumferential direction from the arch top to the arch foot; and four steel bars, namely, a fifth steel bar N5, a sixth steel bar N6, a seventh steel bar N7, and an eighth steel bar N8, are provided at intervals in a circumferential direction from the arch bottom to the arch foot; the second steel bar N2, the third steel bar N3, the fourth steel bar N4, the fifth steel bar N5, the sixth steel bar N6, and the seventh steel bar N7 all exceed the open-cut lining structure 112;

[0098] The vault cross section of the open-cut section lining 120 is provided with first steel plates 111 at intervals along the tunnel direction;

[0099] The bottom cross section of the right-angled inverted arch in the open-cut section is provided with second steel plates 119 at intervals along the tunnel direction;

[0100] The open cut section lining structure 112 is further provided with a row of ninth steel bars N9 and two rows of first and tenth steel bars N10 at intervals;

[0101] In each interval, the first steel bar N1 and the ninth steel bar N9 are welded to the first steel plate 111 , and the eighth steel bar N8 and the first and tenth steel bars N10 are welded to the second steel plate 119 .

[0102] In some embodiments, the lining structure of the underground excavation section is provided with four steel bars, namely, the first steel bar, the eleventh steel bar N11, the first steel bar, the twelfth steel bar N12, and the first steel bar, the thirteenth steel bar N13, at intervals in a circumferential direction from the arch top to the arch foot; and four steel bars, namely, the first steel bar, the fourteenth steel bar N14, the first steel bar, the fifteenth steel bar N15, and the first steel bar, the sixteenth steel bar N16, at intervals in a circumferential direction from the arch bottom to the arch foot.

[0103] In each interval, the first steel bar N11, the first steel bar N12, and the first steel bar N13 are respectively welded to the second steel bar N2, the third steel bar N3, and the fourth steel bar N4, and the first steel bar N14, the first steel bar N15, and the first steel bar N16 are respectively welded to the fifth steel bar N5, the sixth steel bar N6, and the seventh steel bar N7.

[0104] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A tunnel entrance with a semi-blind and semi-light structure combining open and concealed excavation, characterized in that: include: A sleeve arch is arranged at the tunnel entrance, and a guide tube is provided on the sleeve arch within a 60° angle range on the side adjacent to the mountain; A pipe shed comprises steel pipes, which are driven into the surrounding rock along the guide pipe; Cut-and-cover lining structure, including cut-and-cover right-angle invert, cut-and-cover lining and expanded foundation; The underground excavation lining structure includes an underground excavation primary support and an underground excavation secondary lining, wherein the underground excavation secondary lining is located within the inner layer of the underground excavation primary support, and the underground excavation primary support and the underground excavation secondary lining are connected to the open excavation lining; and The counter-pressure backfill structure is arranged outside the right-angle inverted arch of the open-cut section, the lining of the open-cut section and the expanded foundation.

2. The semi-open and semi-dark structure of a tunnel entrance combining open and concealed excavation according to claim 1, characterized in that: Three I-beams are arranged in the sleeve arch; the diameter of the guide tube is 100-150 mm; the three I-beams and the guide tube are welded into a whole.

3. The semi-open and semi-dark structure of a tunnel entrance combining open and concealed excavation according to claim 1, characterized in that: The open-cut section lining structure is provided with first, second, third and fourth steel bars at intervals in a circumferential direction at right angles from the arch top to the arch foot; and fifth, sixth, seventh and eighth steel bars are provided at intervals in a circumferential direction at right angles from the arch bottom to the arch foot; the second, third, fourth, fifth, sixth and seventh steel bars all exceed the open-cut section lining structure. The first steel plates are arranged at intervals along the tunnel direction on the vault cross section of the open-cut section lining; The bottom cross section of the right-angled inverted arch in the open-cut section is provided with second steel plates at intervals along the tunnel direction; The open cut section lining structure is further provided with one row of ninth steel bars and two rows of tenth steel bars at intervals; In each interval, the first steel bar and the ninth steel bar are welded to the first steel plate, and the eighth steel bar and the tenth steel bar are welded to the second steel plate.

4. The semi-open and semi-dark structure of a tunnel entrance combining open and concealed excavation according to claim 3, characterized in that: The lining structure of the underground excavation section is provided with an eleventh steel bar, a twelfth steel bar and a thirteenth steel bar at intervals in a circumferential direction from the arch top to the arch foot; and a fourteenth steel bar, a fifteenth steel bar and a sixteenth steel bar are provided at intervals in a circumferential direction from the arch bottom to the arch foot. In each interval, the eleventh steel bar, the twelfth steel bar and the thirteenth steel bar are respectively welded to the second steel bar, the third steel bar and the fourth steel bar, and the fourteenth steel bar, the fifteenth steel bar and the sixteenth steel bar are respectively welded to the fifth steel bar, the sixth steel bar and the seventh steel bar.

5. A construction method for a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance, characterized in that: include: The slope of the mountain outside the tunnel entrance and between the entrance stake and the light-dark boundary stake shall be set at 1:0.5; A sleeve arch is constructed at the tunnel entrance, and a guide pipe is provided within a 60° angle on the side adjacent to the mountain; A pipe shed is constructed on the sleeve arch, and steel pipes of the pipe shed are driven into the surrounding rock along the guide pipe; The open cut section is constructed to form an open cut section lining structure, wherein the open cut section lining structure includes an open cut section right-angle invert arch, an open cut section lining and an expanded foundation; The counter-pressure backfill construction forms a counter-pressure backfill structure, wherein the counter-pressure backfill structure is arranged outside the right-angle inverted arch of the open-cut section, the lining of the open-cut section and the expanded foundation; and The construction of the dark excavation section forms a dark excavation section lining structure, which includes the dark excavation section initial support and the dark excavation section secondary lining. The dark excavation section secondary lining is located in the inner layer of the dark excavation section initial support, and the dark excavation section initial support and the dark excavation section secondary lining are connected to the open excavation section lining.

6. The construction method of a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance according to claim 5, characterized in that: The open cut construction includes: First, the surrounding rock of the exposed section of the structure is excavated using the step method and vertical temporary supports are set up; Under the protection of the pipe roof and the vertical temporary support, the open-cut section lining structure is cast; the open-cut section lining structure is provided with first, second, third and fourth steel bars at intervals in a circumferential direction at right angles from the arch top to the arch foot; the open-cut section lining structure is provided with fifth, sixth, seventh and eighth steel bars at intervals in a circumferential direction at right angles from the arch bottom to the arch foot; the second, third, fourth, fifth, sixth and seventh steel bars all exceed the open-cut section lining structure; the open-cut section lining structure is also provided with a row of ninth steel bars and two rows of tenth steel bars at intervals; Pre-embedding first steel plates at intervals along the tunnel direction in the arch top section of the open-cut section lining, and pre-embedding second steel plates at intervals along the tunnel direction in the arch bottom section of the right-angle inverted arch of the open-cut section; and In each interval, the first steel bar, the ninth steel bar and the first steel plate are welded, and the eighth steel bar, the tenth steel bar and the embedded second steel plate are welded.

7. The construction method of a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance according to claim 6, characterized in that: The provision of vertical temporary support includes: 16 I-steel arch frames are installed at intervals within the main body of the vertical temporary support; Use 22mm diameter locking coil anchor rods to cross and weld at intervals at both ends of the vertical temporary support body to form a whole; and The middle of the vertical temporary support body is welded with 22mm diameter early strength drug-coated anchor rods at intervals, thus forming a whole with the surrounding rock.

8. The construction method of a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance according to claim 6, characterized in that: The underground excavation construction includes: The tunnel construction is carried out using the fully enclosed underground excavation method, and initial support for the underground excavation section is provided; removing the vertical temporary supports; and The secondary lining of the concealed excavation section is integrally molded; the eleventh steel bar, the twelfth steel bar and the thirteenth steel bar are circumferentially arranged at intervals from the arch top to the arch foot of the secondary lining of the concealed excavation section; the fourteenth steel bar, the fifteenth steel bar and the sixteenth steel bar are circumferentially arranged at intervals from the arch bottom to the arch foot; in each interval, the eleventh steel bar, the twelfth steel bar and the thirteenth steel bar are respectively welded to the second steel bar, the third steel bar and the fourth steel bar, and the fourteenth steel bar, the fifteenth steel bar and the sixteenth steel bar are respectively welded to the fifth steel bar, the sixth steel bar and the seventh steel bar.

9. The construction method of a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance according to claim 6, characterized in that: The exposed section of the structure is first excavated using the step method, and vertical temporary support is set up, including: Excavate the upper surrounding rock of the open cut section; Construct temporary vertical support on the upper part of the open cut section; Excavation of the surrounding rock below the open cut section; and Construct vertical temporary support at the bottom of the open cut section; Before each excavation, hollow grouting anchor rods are used to reinforce the surrounding rock in front of the adjacent mountain side.

10. The construction method of a semi-open and semi-hidden structure combining open and hidden excavation at a tunnel entrance according to claim 8, characterized in that: The tunnel construction is carried out by adopting the fully enclosed underground excavation method and setting up the initial support of the underground excavation section, including: Excavate the upper surrounding rock of the underground excavation section; Carry out initial support on the upper part of the underground excavation section; Excavation of the upper surrounding rock of the underground excavation section; and Carry out initial support on the upper part of the underground excavation section.

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